Fangs
by thekyuubivixen
Summary: Having a vampire as a boyfriend has its ups and downs...but mostly ups. [Sonadow] Added an extra chapter for Sonic's bday
1. Chapter 1

**Disclaimer- I don't own Sonic and co.**

 **It's the spookiest month of the year, and I couldn't help myself. I have zero self-control.**

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When Sonic opened the door, he knew that something was off.

Emerald eyes keenly scanned the undisturbed living room as his brow furrowed. Usually when he returned from his morning runs, he could hear Shadow somewhere in their cozy home. On the rare occasions he came back to an empty house, Shadow's fresh scent would linger in the air.

Now, there was barely a hint of that vampire anywhere.

That meant Shadow hadn't gotten out of bed yet, still sleeping. Sonic gently closed the door behind him as mental alarms went off. It was nearly noon, and Shadow _never_ failed to be up by this time.

Sonic perked his ears and sniffed his nose to make sure he hadn't missed anything. The house was silent, and there was nothing but his own earthy smell.

"Shadow?" Sonic called out and received silence in return. The vampire was a notoriously light sleeper, and the walls here weren't thick. Something was definitely up.

Sonic didn't bother to mask his heavy-set footsteps when he navigated his way to their bedroom. He flung the door open and nearly recoiled from surprise when it stopped mid-swing.

A broken groan barely reached his ears. Sonic's breath caught in his throat.

"Shadow!" He managed to squeeze between the door and the frame, eyes snapping down to the prone figure splayed out on the floor. He gasped as he crouched down by the vampire's side. "Wha… Shadow, what happened?!"

In retrospect, he knew better than to ask because the chance of an actual answer was slim. Shadow was hanging onto a thread of consciousness, eyes faded and glassy when they lethargically met Sonic's gaze. His extremely pale muzzle worked open, but no words left those lips.

At this point, after taking in Shadow's condition, all of Sonic's surprise dissipated. His concern was still through the roof, but he knew _exactly_ what was happening.

"Are you _serious_ , Shadow?" Sonic fought to keep the growl out of his voice, but it was hard because this could've been _avoided_. "I never wanted it to get this bad, but you're so stubborn I swear _._ "

Shadow didn't try to answer this time. His jaw was clenched.

Sonic took a deep breath to calm his nerves. Shadow was going to be fine. No one had somehow attacked him, he wasn't dying – really – and everything was going to be okay.

"C'mere." His voice composed itself, calmer as he gently maneuvered a limp Shadow into his furry arms. Shadow wasn't light by any means, but Sonic easily carried him over to the rustled bed.

He sat on the blankets and maneuvered until his back was up against a wall, Shadow still secure in his hold. That was the one good thing to come out of this situation. Shadow was too weak to fight his help.

Sonic then maneuvered the vampire until he was kneeling in front of him, his only support being Sonic's hands anchoring his sides. Shadow managed to keep his head upright, eyes muddled and breaths ragged. Despite how out-of-it he was, there was a hint of defiance there that had Sonic frowning.

"Why, Shads?" Sonic exhaled harshly at the condition of the strongest person he was lucky enough to know. Lithe yet powerful muscles that could combat the foulest demon barely could twitch by themselves, and the gaze that had caused ghouls and goblins to cower at his feet now wouldn't be able to make a skittish mouse scurry.

Sonic met that stare and gave him a meaningful squeeze; not too hard, but enough to get him to _listen._ "Why are you doin' this to yourself?"

Again, he was met with silence.

Sonic kept his frustration at bay because Shadow didn't need that. He needed blood. A _person's_ blood.

He didn't know why, but Shadow had always sought out wild animals to drink from. That was what had initially drawn Sonic to him. The other few vampires he had run into weren't as people friendly.

When asked about it, Shadow never revealed the reason why, and Sonic let it go. It seemed like the alternate diet was working for him, until he and Sonic got together.

It didn't start immediately, or at least, Sonic didn't notice right away. However, as months went on, he saw that Shadow became more winded, his reaction times gradually slowed, and he would go on more hunts. He would get better, but only temporarily.

Sonic figured that the diet wasn't working anymore.

He had the idea to offer himself up, but Shadow wasn't having it.

Sonic let it go but brought it back up when the vampire's condition was getting worse. Again, Shadow shot it down.

He continuously disregarded the obvious solution until today, because Sonic was going to fix this right _now._

Sonic weaved his fingers into Shadow's head quills, careful of his claws. "I hate seeing you like this." His voice was a near whisper, but his words retained their strength. "You're gonna drink from me," he said with conviction. Those weary scarlets narrowed, but he wasn't deterred. "Whether you want to or not."

He didn't wait for a response because he wasn't going to get one. Sonic carefully brought Shadow against his chest in one swift move, wrapping a solid arm around his lower back and pushing Shadow's muzzle in the crook of his neck.

He felt the vampire's breath stutter against his fur, and the sudden tremble of his weak frame wasn't lost on Sonic. It was obvious that Shadow was battling against every instinct he had not to bite, and Sonic would've been impressed at the self-control any other day.

"I can sit here all day, Shads." Sonic pressed Shadow closer to his body when the shivers strengthened. "So get a little bite, yeah? I promise I won't taste bad."

Sonic's hopes rose when he felt Shadow open his mouth, but instead of sharp fangs, he received a breathy murmur. "Out…side…"

It didn't take a genius to put together the meaning. Sonic shook his head. "No can do. Hunting animals isn't enough for you anymore, and-" The rest of his words died in his throat when a sharp pain emitted from his shoulder. He hissed but refrained from instinctively pushing Shadow off, instead holding him tighter.

Sonic's head thudded against the wall as he gritted his teeth because yeah, the pain was _there._ But there also was the full-on shivers that traveled up and down his spine, the breathlessness as Shadow shifted against him, and the way his toes curled when those fangs dug in deeper.

This couldn't be normal. No way. Sonic had heard screams of absolute terror and _agony_ when someone was attacked by a vampire, not this. Nowhere close to this.

Shadow pressed harder into him, his recovering arms sliding up Sonic's chest and fisting handfuls of long fur. Sonic panted as the vampire huffed against his skin, closing his eyes because he absolutely wasn't expecting this.

Sonic lowered his hand from Shadow's head since it wasn't needed anymore. Instead, relocated to his shoulder blades for comfort and support.

He swallowed thickly when he felt blood trickle down from the wound, some escaping Shadow's mouth. Sonic took the deepest breaths he could as the vampire continued to drink, and he let him until his head started to feel dizzy.

"Hey…" Sonic's voice was more guttural than he remembered, and he cleared his throat. "I know that I'm pretty good, but are you back to a hundred percent yet?"

At first, he believed Shadow was too busy to hear him – or to care – but Sonic winced when the fangs disconnected. A sigh then rushed past his lips when a tongue slowly lapped at his shoulder, probably cleaning up the inevitable mess left behind.

When Shadow eventually sat up, Sonic lazily smiled at the flushed cheeks and the crisp scarlet irises glaring at him. Sharpened canines were bared, still a bit stained, and Sonic chuckled. "See? Not too bad, right?"

"You're a damn _idiot._ " Shadow snarled, and Sonic blinked in confusion when his chest hair was painfully yanked. "You have _no_ idea what you just-" He was speechless when Shadow not-so-gently pushed away from him, growling. "I'm leaving."

"Wha-?" Sonic tightened his hold on him, unsure about what he did, besides the obvious. Shadow was worked up about it though, and he knew just the thing to calm him down. "You can't!" Shadow began to resist; he threw him a wolfish grin. "It's my turn next."

The vampire paused to process that, and Sonic pounced. He quickly leaned forward and tucked his muzzle under Shadow's chin, licking a broad stipe over his Adam's apple. Two hands planted against Sonic's shoulder and squeezed, but they didn't shove him away.

Sonic smirked before peppering kisses down Shadow's jaw and throat, nipping here and there to make his fingers twitch.

Funny how a vampire's weakest spot was his neck.

Satisfied there, Sonic pulled back and gave the vampire a peck on the lips. He grinned at the glare that never let up, but Shadow wasn't making a move to leave anymore. Mission accomplished.

"Now…" Sonic tilted his head, the high from _everything_ still lingering in his system. "Why was feeding from me a bad idea again?"

Shadow crossed his arms with a prominent frown, clearly not happy. "Because I won't be able to feed off of _anything_ else _,_ " he snapped.

Sonic had to be missing something here. "Okay? I don't care, if that's what you were worried about." He chuckled. "I mean-"

And then Shadow was in his face, hissing with his quills bristled. "I could _kill_ you."

Sonic just stared at him until all of it clicked. " _That's_ what you're worried about?" A placating smile grew. "C'mon, Shads! You know how hard it is to kill me!" The vampire wasn't buying it, eyes swirling with heat. "I wouldn't just let you drain me, and you even stopped yourself! You have enough self-control to-"

"I _don't._ " Shadow spat, glaring at the adjacent wall. "If you hadn't said anything, I wouldn't have stopped."

"I don't believe that for a sec-"

"I've done it before." Shadow met his gaze again, and Sonic was taken aback by the guilt mixing in with the hot anger. "You haven't been lost in it. You block everything out while you feed. The struggling, the screams, the _begging_." He clenched his jaw. "You're lost until it's too late."

It was then that Sonic knew. Shadow hadn't limited his hunt to animals on a whim. He had killed someone, someone he regretted to this day.

Sonic closed the distance again, nuzzling Shadow's cheek. "But you heard me," he whispered when the vampire leaned into him. He wasn't going to go into Shadow's past right now. That could wait another day.

His grin was lopsided when he finished. "I can handle it, Shads. Trust me. And plus, I wasn't exactly screaming, was I?" Shadow simply grunted. His anger wasn't as potent anymore, but it was replaced by a far-away look. Sonic wanted to get rid of it so he couldn't be bogged down by bad memories. He asked, "Why was that? You don't really hear about victims kinda enjoying the process…"

Shadow tensed as he glanced away. "Because victims aren't usually mates. The bond formed by the bite makes it…"

He didn't finish, but Sonic didn't need him to. "Oh." His smile widened as his tail wagged. "Aw, Shadow! That's so sweet!" He released an exaggerated sigh. "There's nothing more romantic than sparing me most of the pain of getting my blood drained!"

He laughed and let an exasperated Shadow slide out of the bed. "While you stay here and enjoy your own immature company, I'm going to find demons to kill."

"Love you too!"

Sonic waved at Shadow's back until he disappeared from sight. Then, he gently placed his hand over where he had been bitten. The puncture had healed, but the memory remained clear in his mind.

Mealtimes would definitely be interesting from here on out.

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 **These two will be the death of me, I swear.**


	2. Chapter 2

**Disclaimer- I don't own Sonic and co.**

 **Decided to whip this up for Sonic's birthday! I know it's not Halloween or even October, but eh. I love the werehog too much to care. Enjoy!  
**

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Sonic wasn't home, and Shadow was trying not to think much of it.

He was curled up on the couch in their quaint living room, warm under a blanket and steadily losing interest in the book he was reading. As time went on, each page took longer to complete. He was either zoning out or checking the ticking clock overhead.

Eleven-thirty, it read.

Usually, Sonic was here at his side chatting his ear off about his day, whether it be something as mundane as visiting Tails or rescuing villagers from persistent demons. Shadow would listen as he leaned into the werehog's warmth, letting himself be wrapped up, occasionally contributing to the conversation.

Now, the couch was too empty.

The only late nights they had was when there was imminent danger that couldn't be overlooked; typically ones that involved a particular mustached human who foolishly believed he could outclass seasoned monsters.

There was no news that Eggman had showed his ugly head tonight, or any other troubling occurrences. It was peaceful.

So, where was he?

Shadow closed his book once he realized that he'd been reading the same sentence over and over again. He glanced at the clock once more. Eleven forty-five.

He pensively tapped the cover of the book with his finger before eventually tossing it aside. Untangling himself from the blanket, Shadow stood and headed for the phone. There was a chance that Sonic was visiting Tails for some reason this late at night.

He was within arm's reach of it when he heard the front door creak open. Shadow whipped his head around, irritation clashing with the bubble of relief that rose with Sonic's appearance.

However, those emotions were smothered by caution when he met Sonic's gaze. He didn't smell any blood; however, those once brilliant green eyes were stormy, and the smile underneath them was subdued at best.

"Hey," Sonic greeted, his attention flickering to the clock above. Shadow frowned when he winced, closing the door behind him. "Sorry I was out so late…"

"The hell were you?" Shadow asked, turning fully around. His words lacked the bite they should've had.

Sonic rubbed the back of his neck. He halfheartedly chuckled as he padded over to the couch. "I was out running," he said, plopping down on the soft cushion.

Shadow crossed his arms. That obviously wasn't the full story. "Running," he deadpanned, making sure his doubt was palpable. Shadow went to stand in front of him. He glared down, and his brow furrowed when Sonic averted his gaze. "What are you hiding?"

"I'm not hiding anything!" Sonic gave a wolfish grin, but it fell short. His eyes drifted to the clock again. "Not…really."

Shadow followed his gaze. Eleven-fifty. Already tired of this runaround, he bared his teeth even though he knew that intimidation barely worked on Sonic anymore. "Stop beating around the bush, dammit. Spit it out." It was rare to see Sonic like this, and he needed to get to the bottom of it as soon as possible.

Greens met reds once more. The amount of hesitance and wariness Shadow saw made his features unconsciously soften. There had to be something terribly wrong.

"My…" Sonic heavily exhaled, dropping his gaze again. His ears lowered as he muttered, "My birthday's tomorrow."

Shadow blinked at that, caught off-guard. It was partially because of Sonic's dejected tone and how he seemed reluctant to bring it up, but his surprise mostly came from the fact that Shadow hadn't known about it at _all_. They've been mates for a little over half a year, so he assumed that the date had passed before things had gotten serious.

His frown deepened. "Why are you just _now_ telling me this?" Shadow knew that he wasn't the most outgoing party person in the world, and he understood that his stoicism was off-putting to most, but he assumed that Sonic would at least tell him his _birthday-_

He had fought to keep his expression neutral, but something must've shifted to get Sonic to gasp. "It has nothing to do with you, Shads, I swear!" Shadow remained silent, waiting for him to continue. "I wanted to tell you, but…"

Shadow stumbled forward in shock when Sonic reached out and hugged him close. He was now standing in between the werehog's legs, Sonic's forehead buried in his chest fur.

"What are you-"

"I've been putting it off. Telling you." Shadow felt Sonic's breath against his skin as he quietly spoke. "Not about the birthday itself, but what happens…during it."

He didn't fight the awkward embrace, placing his hands on Sonic's shoulders. "Which is?" he pushed. Sonic held him tighter and mumbled incomprehensibly into his fur. Clicking his tongue in agitation, Shadow pinched one of his blue ears. He felt him flinch. "I can't hear you."

A moment later, Sonic's words were as clear as day. "I have two forms."

Shadow, again, didn't expect the answer. "Forms?" The only creatures he'd known to do have forms were demons, strong ones at that.

"Yeah. This one, and…" Sonic sighed, the warmth spreading across Shadow's front. "…one not so impressive."

"Care to explain?"

Sonic chuckled. It was lacking the usual mirth. "You'd probably laugh when you see it. I get so small and frail and _weak_ compared to now. Nothing like the strong and independent hero you fell for."

He tried to joke to hide his insecurity, but Shadow saw right through façade. Sonic always wore his emotions on his sleeve, the complete opposite of him.

Shadow scoffed. "Do you think I'm that shallow?"

"No!" Sonic nuzzled the fur on his chest. "I just _hate_ the thought of being useless, y'know? I can't do _anything_ in that form. I usually hole myself somewhere on my birthdays, hoping that no one needs my help, that no one gets hurt because I'm not there."

Shadow was starting to understand now. Any failure would resonate in Sonic ten-fold. He swore to protect the people from danger no matter what it took. That drive and confidence was what pulled Shadow in in the first place. Now that there was a form that he couldn't do that in…

"And…I didn't want you to see me like that. Someone who couldn't protect innocents." Shadow felt Sonic's fingers twitch. "Someone who can't protect you."

Something warm and heavy swirled within him. Shadow disregarded it, retorting, "As if I need protection." He'd beat down demons three times his size many times in the past.

Sonic snickered. There was life in it now. "I know, I know, tough guy. But still. It's always nice to have the option."

Shadow simply hummed, checking the time. Less than two minutes to twelve. "I'm guessing that you change exactly at midnight?"

Sonic held him even tighter. "Yeah. Can I hold you like this while it happens? It's not exactly…painless."

The way Sonic's voice shook at the end told Shadow that his high pain tolerance didn't cover this. He didn't answer, instead sliding his hand around the back of Sonic's head, digging his fingers into the thick fur there.

"Thanks," Sonic murmured, and they waited.

It started with a sickening crack that made Shadow's breath hitch. Sonic's own breaths grew raspier, and he winced when claws began scratching at his back. Shadow blocked the pain out, watching, speechless, as Sonic's muscles convulsed and bones snapped under rippling fur.

Shadow swallowed thickly when Sonic cried out, writhing against him. He could do nothing but support him as the werehog's coarse fur was replaced with smooth quills, as his body contorted and shrunk, and as his pained growls became higher and higher pitched.

The transformation barely lasted a minute. Shadow was still wrapped in Sonic's grasp, but it was noticeably weaker than before. Ragged breaths fanned across his stomach now instead of his chest.

He waited a moment before carefully removing his hand from the bed of bristled quills, gaining small cuts in the process. Again, he pushed the pain away in favor of stepping out of Sonic's hold.

There was little resistance. Weakened arms slipped from around him, falling to the couch. Sonic's head was lowered, his chest was heaving, and his fingers were trembling.

Shadow took this time to look him over. Sonic hadn't been lying about his description, because his size about half of what it used to be. He wasn't small by any means, however. His frame was near identical to Shadows, except he was a bit leaner.

His arms and muzzle were now covered in short peach fuzz, his hanging quills reached down his back, and his fur was the most _brilliant_ shade of blue he's ever seen. It was a bright azure color, sharply contrasting the navy blue it was before.

His silence must've lasted too long, for Sonic sighed. "It's a lot to take in, I know." His voice wasn't as raspy, missing the low rumble that usually accompanied it. "It's gotta be jarring knowing that _this_ is under the hero that…"

Shadow lifted Sonic's chin with his finger, causing him to trail off. He searched his mate's stunning green eyes, the azure fur making them shine more.

Sonic held his gaze as well. Insecurity swirled in those emerald pools when he whispered, "Shadow…?"

"You talk too much," he muttered before leaning down and capturing Sonic's lips with his own. Sonic stiffened before melting into it, sighing out of his nose.

Their mouths molded together perfectly, languidly brushing against each other. Shadow made sure that Sonic understood that he was _his._ It didn't matter what he looked like because Sonic was still Sonic. The confidence, the stubbornness, the supportiveness, and the softness that made Sonic _Sonic_ didn't rely on appearance.

His view of the hero wouldn't change just because he looked like this.

Though, this form wasn't exactly hard on the eyes either.

Shadow had a hard time expressing how he felt with words, so he poured it all into the kiss.

And Sonic seemed to interpret it correctly. He smiled against his lips before snaking his hand around Shadow's neck, bringing him closer. Shadow allowed Sonic entrance at the silent plea, humming as their tongues intertwined together.

It was different, of course. Sonic wasn't as rough – not that was bad, per say – as before and there was a smaller chance of Sonic nicking himself on Shadow's sharp fangs.

The passion hadn't dissipated, however. Shadow was left near breathless when Sonic pulled back with a broad smile and flushed cheeks. "Thanks, Shads, I…"

Not done yet, Shadow moved up and planted a chaste kiss on Sonic's forehead. "Happy birthday, Sonic," he muttered against the fur there.

Shadow then straightened up, feeling lighter at the amount of emotion aimed at him. Sonic opened and closed his mouth a few times before a laugh bubbled out of his throat.

He stood up and hugged Shadow, causing the vampire to take a step backwards. This was different too, Shadow noticed. He wasn't completely encompassed in warm fur, and there weren't built muscles embracing him, but…

Shadow wrapped his arms around Sonic as well, pulling him impossibly closer.

"Guess I was stupid for worrying, huh?" Sonic muttered before resting his head on Shadow's shoulder.

"Wouldn't be the first time you did something without thinking," he lightly teased and felt Sonic's chuckle rumble against his chest. Shadow let the hug last a few more moments before loosening his grip. "Now, stop being so mushy and get off me."

Sonic was grinning as he did so, and Shadow absently noticed that they were the same height. "Says the one who gave me a forehead kiss. Gettin' soft on me, Shadow?"

"Not like you are." He squeezed Sonic's upper arm, and the hedgehog pouted. "You didn't keep any residual powers? Like your elasticity?"

"Nope. Basically a regular civilian now." Sonic sighed. "Really sucks, but I'll get through it. I've done it for this long."

Shadow recalled him mentioning being holed up on his birthdays, and he could see why. Villains would have a field day if they figured out that Sonic was like this, basically defenseless. Sure, Sonic most likely had been with friends on past birthdays, but still. This information would be dangerous if it spread.

He was going to protect it – and him – with his life.

"Should I expect company when we wake up?" Shadow asked, wondering if he needed set up their home for anything.

Sonic waved him off. "Nah. I usually celebrate my birthday the day after."

Shadow rose an interested brow. "So, I have you all to myself tomorrow?"

"Yep, so you better get to planning!" The hedgehog poked his chest with a smirk. "I know it's short notice, but I'm sure you can figure out _something_ we can do to celebrate." He winked, and Shadow already had a couple things in mind.

A loud ringing pierced the air, and they both glanced over to the phone. Sonic perked up. "That must be Tails!" He jogged over and answered it, "Hey, little bro!"

Shadow watched him animatedly talk over the phone, the ghost of a smile growing on his face.

This birthday was going to be one to remember. He would make sure of it.

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 **Hoped you all liked it!**


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